The present invention relates to a method of manufacturing a blade constituted of composite materials adapted for a rotary wing of a helicopter.
A conventional technology for manufacturing a composite material blade is disclosed in, for example, Japanese Patent Publication No. 58-4679, in which a main spar member and a hollow expandable member are arranged between upper and lower skins made of a resin located in a mold assembly in a condition where the main spar member and the hollow expandable member are enclosed by a band-like member. The skins are then subjected to thermo-setting treatment, while applying pressure to the interior of the hollow expandable member, to integrate the main spar, the hollow expandable member and the skins.
This conventional composite material blade manufacturing method requires accurate control of the pressure to be applied. Further, in an adverse case, a core member arranged between the upper and lower skins may be crushed by the high pressure in the hollow expandable member. In addition, since a reinforcing member is merely disposed, without being fixed, to a predetermined position in the molding operation period, the reinforcing member may be pushed outward by the compression force of a mold assembly after closing the mold assembly, resulting in crushing the core member.
Another conventional technology is disclosed in, for example, Japanese Patent Laid-open Publication No. 60-234833, in which an outer skin structure and a hollow inner mold having a closed section in which a core member is disposed, are arranged on molding surfaces of a mold assembly and a compression force is then applied to the core member by the mold assembly to integrally form the outer skin structure, the inner mold and the core member while applying pressure and heat thereto.
In this method, substantially the same problems as that of the first conventional method will be encountered.
A further conventional technology is disclosed in, for example, Japanese Patent Laid-open Publication No. 60-166592, in which an elongated member preliminarily formed by thermo-setting treatment in a specific mold assembly is prepared and the elongated member is integrally formed with a rear side mold member formed independently from the elongated member with an outer cover by a joint coupling technique.
In this conventional blade manufacturing method, at least two mold assemblies are required, resulting in the increase of manufacturing cost. In addition, the products thus manufactured may have variable dimensions and shapes due to the manufacturing errors in the mold assemblies, thus making it difficult to increase the quality of the products.